Reconciliation of Segment Revenues and Operating Profit to Consolidated Income from Operations (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Segment Reporting Information [Line Items]
Revenues	$ 103,800	$ 80,176	$ 198,183	$ 152,978
Income from operations	16,830	10,878	30,614	22,690
Stock-based compensation expense	(1,773)	(655)	(3,323)	(1,369)
Depreciation and amortization	(2,423)	(1,959)	(4,634)	(3,649)
Goodwill impairment loss		(1,697)		(1,697)
Operating Segments
Segment Reporting Information [Line Items]
Revenues	103,776	80,086	198,147	152,779
Income from operations	22,061	16,745	40,967	31,431
Unallocated Amount to Segment
Segment Reporting Information [Line Items]
Revenues	24	90	36	199
Other revenues	24	90	36	199
Stock-based compensation expense	(1,773)	(655)	(3,323)	(1,369)
Legal settlement			(640)
Non-corporate taxes	(514)	(1,015)	(1,239)	(1,595)
Professional fees	(889)	(1,083)	(1,318)	(1,381)
Depreciation and amortization	(151)	(246)	(308)	(476)
Bank charges	(296)	(180)	(545)	(329)
Goodwill impairment loss		(1,697)		(1,697)
Other corporate expenses	$ (1,632)	$ (1,081)	$ (3,016)	$ (2,093)